The period treated in this thesis is one which is often characterized as a transition between World War II and the Cold War. By approaching it instead as a window of opportunity – a period in which the governments of small states perceived both an unusual space and an urgent need to reevaluate security – the security policies of two small northwestern European countries, the Netherlands and Sweden, are subjected to a critical reappraisal. Through a systematic comparison of the security ideas and strategies in two countries that ended up with different positions on alignment/non-alignment during the Cold War, this dissertation sheds new light on the reasons for the development of those security policies as well as on their significance. Not only does it uncover a number of concrete security strategies that were remarkably similar regardless of different circumstances, but it shows that the Swedish and Dutch governments formed similar ideas about the needs for future security in spite of different war experiences. Both concluded that small states could no longer survive in isolation and instead aimed for a better functioning system of collective security, built on the close cooperation of regional groups. This thesis argues that the different choices regarding security in 1948, when the Dutch signed the Treaty of Brussels and the Swedish reclaimed a policy of non-alignment, were in fact motivated by the same wish to maintain as wide a margin for manoeuvre as possible for the cooperation envisioned during the war, seeing this as the best guarantee of peace and independence.